Hi
pretty much anything with a chest band will be sufficient. I'd say that one of the issues I've seen for ladies (certainly my wife) is that the location is often "in the way" of their sports bra. so this can present a challenge but with some thought you can get it strapped in and maintaining good contact.
Personally I also like the Garmin Vivofit system as its low cost and reports lots of useful stuff (including sleep if I was to wear the watch thing at night).
I've used even basic $40 watches with chest bands in the past, but the modern stuff also keeps all your records for you (as long as you sync it) but you have the drama that its "online" and "who knows who's seeing it"
As a result I don't use my real name there (well or here really).
Myself I prefer the Garmin watch over the others because it has a 6 month battery life (they claim 'up to a year', but I assume that's if you don't use it) and stores 20 days worth of data if I'm not an obsessive complusive syn'er needing to see how many steps I did in the last 10 seconds (every hour of the day).
So this means I can essentially forget about it for over a week. As it happens I also chart my active KCal as part of my weekly INR monitoring, so I usually sync weekly.
this review was what sold me on the Vivofit
http://www.dcrainmaker.com/2014/03/g...it-review.html
I've changed (wrist) bands and they're available on eBay for like $5 ... this is not an insignificant point because some have "single unit" bands that are not replacable and one of the guys with a microsoft watch has had the band start to break after 4 months ... he's not a happy camper.
I go for the best bang for buck at the lowest price so if you loose it you're not weeping tears of blood (well and I'm on warfarin so imagine how that would end ... drowning in tears?)